I'd look at differences in engine hours, wear and tear, propeller, governors, rigging and the like before I went to work on black leading edges which probably do more to protect from stone strikes than degrade performance in the heat. My aeroplane is dark blue but it goes faster, climbs better and uses the same fuel than lighter colored versions I've seen. The only difference I can see is I have a TAS ASI and OAT. The others an IAS ASI. I'll leave it to the 'real experts' on PPRune to guide you on influence on aerodynamics.